Pennsylvania · 25 Pa. Code §73.31
Septic system requirements in Pennsylvania
Tank sizes, drainfield rules, setbacks, permits, and real costs — pulled from Pennsylvania's own code rather than a national average.
- 3-bedroom tank
- 1,000 gal
- Design flow
- 100 gpd/BR
- Typical install
- $10,000–$28,000
- Permit fee
- $300–$1,200
- Well setback
- 100 ft
- Permitted by
- County / local
Septic tank sizes required in Pennsylvania
Pennsylvania sizes systems on a design flow of 100 gallons per day per bedroom, with every dwelling rated for at least 3 bedrooms. The tank must meet both the bedroom table below and a 2× daily-flow detention requirement — whichever produces the larger number governs.
| Bedrooms | Design flow | Code minimum | Recommended |
|---|---|---|---|
| 1 bedroom | 300 gpd | 900 gal | 1,000 gal |
| 2 bedrooms | 300 gpd | 900 gal | 1,000 gal |
| 3 bedrooms | 300 gpd | 900 gal | 1,000 gal |
| 4 bedrooms | 400 gpd | 1,250 gal | 1,250 gal |
| 5 bedrooms | 500 gpd | 1,500 gal | 1,500 gal |
| 6 bedrooms | 600 gpd | 1,750 gal | 2,000 gal |
Source: 25 Pa. Code §73.31. The recommended column rounds the governing requirement up to a tank size manufacturers actually stock.Run your own numbers →
Drainfield size and cost by soil type
For a three-bedroom home in Pennsylvania at 300 gpd. This single table explains most of the variation between quotes — the area scales inversely with how fast your soil accepts water, and the drainfield is the largest line item in the job.
| Soil | Loading rate | Absorption area | With reserve | Typical total install |
|---|---|---|---|---|
| Medium sand | 0.8 gpd/ft² | 375 ft² | 750 ft² | $10,400 |
| Sandy loam | 0.5 gpd/ft² | 600 ft² | 1,200 ft² | $12,500 |
| Loam | 0.4 gpd/ft² | 750 ft² | 1,500 ft² | $13,900 |
| Silt loam | 0.3 gpd/ft² | 1,000 ft² | 2,000 ft² | $16,200 |
| Clay loam | 0.2 gpd/ft² | 1,500 ft² | 3,000 ft² | $20,900 |
Estimates use Pennsylvania's cost index of 1.04× the national average. Build a line-item estimate →
Permits and who issues them
A municipal Sewage Enforcement Officer issues the permit under DEP Chapter 73. The SEO, not the township engineer, is the decision-maker.
| Permit required | Yes |
|---|---|
| Typical fee | $300 – $1,200 |
| Soil evaluation | Required before permit |
| Licensed installer | Not required statewide |
| Turnaround | 3–8 weeks |
| Ongoing inspection | Not mandated statewide |
| Reserve area | 100% replacement area required |
Minimum setback distances
Measured horizontally from the drainfield unless noted. Local rules are frequently stricter, and on a small lot these numbers — not the soil — often decide the layout.
| Private water well | 100 ft |
|---|---|
| Well (septic tank) | 50 ft |
| Property line | 10 ft |
| Surface water | 50 ft |
| Building foundation | 10 ft |
Regulatory contact
Pennsylvania DEP — Bureau of Clean Water, Sewage Planning
www.dep.pa.gov · 717-787-8184
What makes septic hard in Pennsylvania
Shallow bedrock and fragipan across much of the state restrict both depth and percolation.
Limestone valleys in the south-central counties are karst, with rapid groundwater connection and strict siting.
Act 537 sewage facilities planning can require a formal plan revision before a permit is even considered, which adds months.
Things that catch people out
- Pennsylvania's 400 gpd minimum design flow for three bedrooms or fewer explicitly includes the allowance for a garbage grinder, washer, dishwasher, and water softener — so there is no separate disposal uplift.
- If your lot needs an Act 537 plan revision, budget several extra months and several thousand dollars before the septic permit itself.
Pennsylvania septic questions
What size septic tank do I need in Pennsylvania?
A three-bedroom home in Pennsylvania requires a minimum 900 gallon tank under 25 Pa. Code §73.31. Design flow is 100 gallons per day per bedroom, and the tank must also hold 2 times daily flow, so the practical recommendation is 1,000 gallons.
Do I need a permit for a septic system in Pennsylvania?
Yes. A municipal Sewage Enforcement Officer issues the permit under DEP Chapter 73. The SEO, not the township engineer, is the decision-maker. Fees typically run $300 to $1,200, with a turnaround of about 3–8 weeks. A soil evaluation or percolation test is required before a permit is issued.
How much does a septic system cost in Pennsylvania?
A conventional system for a three-bedroom home typically runs $10,000 to $28,000 installed. Soil quality moves this more than anything else — on tight clay requiring a mound, budget two to three times the low end.
How far must a Pennsylvania drainfield be from a well?
100 feet from a private water well, with the septic tank itself allowed at 50 feet. Local rules can be stricter.
Sources
Every figure on this page traces to one of these documents.
- 25 Pa. Code §73.31 — Standards for septic tanks · verified 2026-09-18
- 25 Pa. Code Ch. 73 — Standards for Onlot Sewage Treatment Facilities · verified 2026-09-18